Teacher's day is celebrated all in India on 5th Sept on the birthday of Dr S Radhakrishnan as a day to give tribute & thank all the teachers who have been in a great way responsible for the growth of every individual.
Would it make any change if change it as Guru Utsav, and the answer is NO.
In today's generation more than half the students do not have any respect for their teachers. It is a very common thing for the students to comment or talk in a disgraceful manner about their teachers. A lot of them don't find the teachers to be worthy of teaching & in quite a few cases it's actually true.
At school level, we see & read about many teachers working in Government run schools who don't even attend the schools for months but get paid well enough. At college level it's a common practice for graduates who haven't been successful in any job interviews to end up as teachers where they aren't motivated enough to do the job and hence not getting the appropriate respect from students.
A couple of decades ago teaching was a service, now it's just a profession.
Simultaneously we have teachers who devote their time in every which way to impart knowledge among their students. They put their heart & soul in bringing out the best among the children they teach. And these teachers are always the favorites of their students.
In the real world students wait for 5th September as a day where they could pretend to be teachers and enjoy the day, gone are the days where students were afraid of their teachers, when they obeyed their teachers, when they respected their teachers. And in such a world there isn't any real meaning left in celebrating teacher's day let alone renaming it as Guru Utsav.
Even though it is nationally called as teacher's day, every region calls it in a different name in its native language. In Hindi speaking states teacher's day is shikshak divas, in Tamilnadu it is aasiriyar dhinam. So I don't think there isn't any necessity to complicate it more by calling it as teacher's day as the colloquial term is not going to change.
Calling it Guru Utsav has already invited criticism from states where it is seen as one of the ways to impose Hindi as a language on one and all. I feel it would bring in more problems & negation towards Hindi as a language from the non Hindi speaking community all over the country.
The only way we can dignify our teachers is by teaching the children at home to respect the teachers at school or college and making sure that teachers do their work in a manner that they earn respect for the work they do and not by renaming teacher's day as Guru Utsav.